Who rules the Italian city-states in the 13-16th century?

Each city-states had their own rulers. Some of the princely ones where: Florence, Venice, Milan, Rome, Naples, and all of these had rulers like Medici, Doge, Pope, etc.

You can also understand this by the definition of city-states itself. A city-state is an area which is rules on is own by major cities. They had a mix of both hereditary rulers as well as elected rulers. :D

it depends on which society you are referring to. many civilization performed rituals so the gods would with their growing season but the most well known is that of the aztecs. they would make sacrifices, usually animals, but sometimes humans as well.